Full Text:   <491>

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CLC number: TV81

On-line Access: 2018-07-04

Received: 2017-04-14

Revision Accepted: 2017-10-13

Crosschecked: 2018-06-06

Cited: 0

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Citations:  Bibtex RefMan EndNote GB/T7714


Jin-xiao Zhao


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Journal of Zhejiang University SCIENCE A 2018 Vol.19 No.7 P.544-556


A simple method for calculating in-situ settling velocities of cohesive sediment without fractal dimensions

Author(s):  Jin-xiao Zhao, Guo-lu Yang, Monika Kreitmair, Yao Yue

Affiliation(s):  School of Water Resources and Hydropower Engineering, Wuhan University, Wuhan 430071, China; more

Corresponding email(s):   jxzhao@nhri.cn

Key Words:  Dredge, Sediment settling, Porosity, In-situ measurement, Density function

Jin-xiao Zhao, Guo-lu Yang, Monika Kreitmair, Yao Yue. A simple method for calculating in-situ settling velocities of cohesive sediment without fractal dimensions[J]. Journal of Zhejiang University Science A, 2018, 19(7): 544-556.

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author="Jin-xiao Zhao, Guo-lu Yang, Monika Kreitmair, Yao Yue",
journal="Journal of Zhejiang University Science A",
publisher="Zhejiang University Press & Springer",

%0 Journal Article
%T A simple method for calculating in-situ settling velocities of cohesive sediment without fractal dimensions
%A Jin-xiao Zhao
%A Guo-lu Yang
%A Monika Kreitmair
%A Yao Yue
%J Journal of Zhejiang University SCIENCE A
%V 19
%N 7
%P 544-556
%@ 1673-565X
%D 2018
%I Zhejiang University Press & Springer
%DOI 10.1631/jzus.A1700185

T1 - A simple method for calculating in-situ settling velocities of cohesive sediment without fractal dimensions
A1 - Jin-xiao Zhao
A1 - Guo-lu Yang
A1 - Monika Kreitmair
A1 - Yao Yue
J0 - Journal of Zhejiang University Science A
VL - 19
IS - 7
SP - 544
EP - 556
%@ 1673-565X
Y1 - 2018
PB - Zhejiang University Press & Springer
ER -
DOI - 10.1631/jzus.A1700185

The settling velocity of sediment flocs is central to the study of the transportation process of contaminants in aqueous ecosystems. To describe the irregular shape of flocs, fractal theory based on the image analysis method is commonly used. However, this method usually leads to non-unique results as it requires the selection of a threshold intensity. Therefore, the main objective of this study is to develop a method to determine the settling velocity of both flocs and particles without using the fractal dimension. To achieve this goal, porosity was introduced as a substitute for the fractal dimension, and a simple method with three variables, floc diameter, mass concentration, and volume concentration of flocs, was developed. A density function method was used to obtain the floc porosity from a laser particle sizer which could obtain the volume concentration of sediment and an optical backscatter point sensor (OBS). Laboratory tests on two sediments from two different lakes were conducted. Results indicate that this method has a higher accuracy than traditional methods such as the Stokes equation and the Rubey equation. The variable density function performed better than the uniform density function and was, therefore, recommended for calculating the settling velocities for both micro and macro flocs. Using the developed method, the drag coefficient for the flocs was calculated and its accuracy analyzed. The method presented in this paper, which is simpler in determining in-situ settling velocities than traditional methods, also allows for direct inter-comparison between results derived from various studies.


创新点:1. 推导出了不含有分形维数的泥沙絮团沉速公式; 2. 将LISST等高精度仪器应用于泥沙絮团密度计算中.
方法:1. 通过理论推导,得到不含分形维数的粘性细颗粒泥沙沉速公式; 2. 通过试验对该公式的精度进行研究,并在此基础上研究不同密度计算方法对该公式精度的影响; 3. 研究不同沉速状态下,泥沙絮团的沉降规律.
结论:1. 通过对比实测沉速与计算沉速的结果可以看出,本文提出的絮团沉速公式在计算泥沙絮团的沉速时精度较高; 2. 通过比较两种不同密度计算方法的结果可以看出,变密度方法具有更高的精度; 3. 通过拟合结果可以看出,公式(15)中的参数η与泥沙所处的沉降区间有关,参数γ与泥沙自身的性质有关.


Darkslateblue:Affiliate; Royal Blue:Author; Turquoise:Article


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